They're about a 45 min drive apart, so why not do both? The views from Prewitt Ridge are spectacular and plenty of great spots to set up camp. The road to cone peak faces east, so you don't get the same exposure to the pacific. I'd recommend driving to the Cone Peak trailhead, hiking to the peak (I think it's like 1-2 miles), and then heading over to Prewitt Ridge to set up camp.